A force balance model was developed to predict the effects of particle size, particle size distribution and surface potential on the structure of the filter cake. The model predicts that a stable filter cake is formed at low surface potentials and that the filter cake becomes unstable when the surface potential is larger than 30 mV. The model predicts a minimum porosity and permeability for filter cakes formed at intermediate surface potential. The surface potential that produces the lowest porosity increases with increasing particle size in the system. The specific resistance of the filter cake was a function of particle size and surface potential. The surface potential for the maximum specific resistance in the uniform particle system agreed with reports in the literature.